Vulcanizable copolymers of isobutylene and 10-70 per cent combined butadiene



Patented Aug. 19, 1952 VULCANIZABLE COPQLYMERS F ISOBU- TYLENE AND -70 PER CENT COMBINED BUTADIENE Joseph F. Nelson, Clark Township, Union County,

and Lester Marshall Welch, Madison, N. J., assignors to Standard OiLIlevelopment Company, a corporation of Delaware Application November 28, 1947, Serial No. 788,640

This invention relates to low temperature polymerization processes and products; relates particularly 'to the'copolymerization of isobutylene unsaturated, rubbery copolymer; and relates especially to the low temperature copolymerization of isobutylene with a diolefin such as butadiene to produce a copolymer having an iodine number within the range between 50 and 175.

It'has previously been found possible to produce a series of very'valuable copolymers orinterpolymers'from a mixture of a major proportion of is'obutylene with a minor proportion of a C4 to C14 multi olefin having more than one carbonto-carbon double linkage. The procedure utilizes the steps of cooling the mixture to a temperature between 0 C. and 164 C. then polymerizing the cold mixture by the application thereto of a dissolved Friedel-Crafts catalyst. This reaction has been conducted with isobutylene in major proportion and butadiene in minor proportion in the mixture, to yield an excellent polymer which, when cured, showed good strength and excellentphysical properties.

This polymer usually shows an iodine number between about 1 and '1 0. An iodine number of thi value is sufficient to permit of a curing reaction to produce a tensile strength ranging from 1800 to 3600 poundspersquareinch at break. This polymer shows a phenomenally high resistance to the passage through it of air, and it has been found to be particularly useful for autois established that a minimum Staudinger molecular weight number of about 20,000 is required in any event, and an iodine number of at least 0.5.:

However, these requirement are to a considerable extent mutually incompatible. It 'is 'well settled that the diolefln, as such,exerts a definite poisoning action on the catalyst and the largerthe quantity of diolefin present, the more powerful .the poisoning action; this poisoning action This minimum is certainly more than 4 and probably more; than .8. However, .it v

8 Claims. (Cl. 26085.3)

serving primarilyto reduce-the obtainable molecand a multi olefin to yield a relatively highly ular weight of the polymer. copolymerizability varies among the various diolefins. The ratio of copolymerizability of butaiidiene is relatively quite low; a ratio of 30 parts much higher, approximately 3 parts of isoprene per 100 of isobutylene being sufficient to put 1 centage (on the isobutylene) is raised. This is well shown in Figure 1 in which a family of curves for varying ratios of isobutylene to butadiene are shown. A desirable Mooney viscosity for satisfactory milling, calendering and "moulding lies in the neighborhood of 40t0'55'since values below 25 show a polymer too soft for satisfactory handling, and values above are too tough to be milled. It should be noted further that the lower the ratio of the diolefin,butadienethe lower the iodine number andthe poorer and lower the curing properties. curves that a mixture'containing a butadiene to isobutylene ratio, of 25 to (ratio of 0.25) yields an average Mooney value of 40 at 87% conversion, but the' iodine number of this polymer i so low. as 'to'makeit extremely slow curing, of very low' modulus, and a generally unsatisfactory polymer. It will be noted that when the butadiene ratio is raised to 43 parts of butadiene per 100 of isobutylene' (a ratio. of 0.43), the permissible conversion ratio for a 40 Mooney value is about 42 This material is readily curable and is a reasonably good polymer, although it still cures undesirably slowly and to an undesirably low modulus. v It may further benoted that if the feed ratio is increased to-67parts of butadiene per 100 of isobutylene (a ratio of 0.67), the

very first bit of polymer-producedl asa Mooney value of about 27, almost 'too low to be satisfactorily curable. These values seemed to indicate conclusively that the amount of butadiene present mustbe kept below'a ratio of 0.5 to produce usable polymer, and all workers in, the-field=have 1 so understood.

Also, the ratio of a It will be observed from the gem-564 According to the present invention, it is now found that if the polymerization mixture is prepared with a relatively large amount of butadiene present, preferably with a butadiene/isobutylene ratio between 2 and 10, and the amount of polymer produced is preferably limited to' a conversion of 40 or 50% based on the amount of polymerizable feed, an excellent polymer is obtained. The resulting polymer shows an iodine number ranging from 60 to 175; shows a very much shorter curing time and a much higher modulus, as well as many other valuable properties. r

The polymers of the invention contain from 30% to 85% or 90% copolymerized isobutylene with from 70% to copolymerized butadiene, a relatively very large proportion of butadiene thus being copolymerized into the polymer by the application to the high ratio mixture of a Friedel-Crafts catalyst in solution in a low-freezing,

non-complex forming solvent; in the presence of from one volume to five volumes of diluent,.or

no "diluent as desired. The polymerization procedure shows the unexpected and conspicuously advantageous phenomenon of i an increase in average molecular Weight and Mooney viscosity with increasing conversion. Thus, as shown in Fig.2, a ratio of butadiene to isobutylene of 2.5 that is, 25 volumes, of butadiene to 10 volumes of isobutylene yields, at a 30% conversion (onthe amount of isobutylene present) a polymer having a Staudinger molecular weight number of about-14,000 and a Mooney viscosity of about 22; whereas, if the conversion is increased to 56% on the amount of isobutylene present,- the Mooney viscosity value of 35 is reached; and if the con versionis carried to 90% or above (based on the isobutyle'ne) a molecular weight of- 69,000 and a Mooney viscosity of nearly 50 is obtained; (It

maybe noted that this procedure leaves a con siderable amount of butadiene unpclymerized,

unpolyme'rized isfmuch less than in the j prior art," and the polymer is of much more satisfactoriy quality, being faster curing, to higher modu- Thus lus material of higher tensile strength.) these values for the polymer of the presentinvention' are an iodine number between 60 and 175' anda Staudinger molecular weight number within the range between about 20,000 and 100,000, which is curable to a substance having a tensile strength within the range between 700 and 3600 pounds per square inch; with'an elongation within the range between 150% and 1000%,at break; a markedly improved modulus and a curing speed much higher than'that of a copolymer having an' iodine number below 10.

Other objects and details of the invention .will'be following description; in

tweenthe two with respect to thequa-lity of the polymer produced. 7 I

In either process, there is first prepareda mix ture of isobutylene and butadiene 'in which the butadiene is present in a ratio of at-least two with'respect to the isobutylene, thelimiting ratios being from 2 to 10 or 12 times as much butabut 'theto'tal amount "of' isobutylene, remaining 4 diene as isobutylene. It is desirable that rela tively high purity components be used, the isobutylene desirably being at least 98% purity and the butadiene desirably at least 96% purity, preferably-98.5% purity when possible, since the reaction proceeds more satisfactorily with chemicals of such purity. It may be noted that the presence of small amounts of saturates such as butane and propane is immaterial, but the presence of propylene, butene-l or butene-2 is undesirable. V 1

This mixture may be polymerized as such, if desired, but usually, superior results are obtained by polymerization in the presence of a diluent.

freezing point of the'diluent be below thelpoly merizatio'n temperature. 7

For the diluent, the requirements are, gener ally, merely that the substancebe a liquid at the polymerizable temperature and that it be nonreactive with the unsatur'ates and with the catalyst. If it is reactive with the unsaturates, it of course ceases to be a diluent, and if it is reacp-ftive with the catalyst, it ceases to be a diluent for the reason that it becomes a'catalyst poison; Particularly, any carbon containing substancewhich is liquid at the polymerization temperature and'is free from oxygen, is more or less suitable for use as the diluent. Accordingly, the

diluent may properly be defined as a non-'oxy genated, carbon containing compound, having'a'" freezing point below the polymerization ,tem-

perature." In general, such substances arefree from catalyst 'poisoningefie'cts, but the freedom desired temperature} from catalyst poisoning action is essential tothe- "diluentfi In; general also the requirements for the diluent are closely similar to those for" the catalystsolvent subsequently described in that the'diluent also" must be low freezing and non complex forming with 'thef Friedel-Crafts active metal halide substance. i

Either before or after mixing, the materials are 'cooled'to a temperature below about '6=C.' preparatory to the, polymerization procedure. For the polymerization reaction, the preferred temperature lies-below GC,' and preferably withinthe' range between about 40; C. and -103 to ll0 C. or even-"as low as --f16 l'- C."

The coldmixture is placed in a'reactor vessel whichlm'ay' consist of a batch type or a continuoustype reactor. In'either reactor, it is usually or'the like. Highly satisfactory refrigerants are liquid ethane, setting a temperature of -88 (3., and liquid ethylene setting a temperature of 103 10. In both cases,the necessary tempera-" ture gradient through the walls of the container yield-a temperature in; the reaction mi'x'turefrom 2 to'-l'0' C. higher, but this temperature gradient rides.

isnot-harmful. In some instances, liquid methane under pressure may be used or some of the higher. boiling refrigerants under reduced pressure or vacuum may be used.

Alternatively, an internal refrigerant may be used, for which purpose it is necessary that the mixed boiling point be within the desired range and that the internal refrigerant be inert and non-reactive with respect to the Friedel-Crafts catalyst. Liquid or solid CO2, liquid ethane, and liquid ethylene all meet these. requirements and are the preferred internal refrigerants. v Thereaction mixture is polymerized by the application thereto or a Friedel-Crafts active metal halide catalyst in solution in a low-freezing, noncomplex-forming solvent. The preferred catalystisaluminum chloride. Various other active metal halide substances are also usable includ ingaluminum bromide, the mixed chloro bromides especially of aluminum and of titanium, the chloro alk-oxides, especially of aluminum, and the like. These catalystscannotbe used in solid form, however, because of the low solubility of the solids in the olefinic material or the low rate of solution which permits particles of solids to be surrounded by a verythin layer of polymer which thereafter prevents further solution and further polymerization Accordingly, it is essential that when a solid, curable polymer is to be made, the catalyst be fluid. Titanium tetrachloride is fluid at roomtemperature and fluid at a low enough temperature to be readily incorporated into the unsaturate mixture. The other catalyst substances are readily soluble to a satisfactory concentration in the chloro substituted Ialiphatics or in some instances in the hydrocarbons themselves to. produce excellent catalyst solutions which'are'readily incorporated into the polymerization mixture. 7 I

For the catalyst solvent, any non-complexforming solventlwhich is liquid when first contacted with the cold reaction mixture and which will dissolve appropriate amounts of the Friedel- Crafts active metal halide catalyst .is suitable. For the purposes of this disclosure, any substance having a freezing point below 0 C. is lowfreezing, and any substance which does not cause to separate from the solution, upon evaporation of the solvent, a compound between the solvent and the Friedel-Crafts catalyst; or with which the addition to, or evaporation from the solution of portions of the solvent leads to a subthe solvent, is non-complex-forming.

Particularly useful are ethyl and methyl chlo- Similarly useful solvents are such substances as carbon disulflde, methylene dichloride, ethylene di-chloride, chloroform, triand tetrachloroethane, ethylidene fluoride, some of the organic chloro fluorides, and the like. Also with such catalystsas aluminum. bromide, aluminum bromo-chloride, aluminum chloro-ethoxide, and

the like, the lower boiling hydrocarbons are preferably obtained' b'ya refrigerating jacket uponthe reactor, but,.as above pointed out, this is not necessary.

- If the reaction is to. be conductedin aseries of successive batch operations, the. appropriate mixture of unsaturates maybeprepared and stored ata reduced temperature until needed, successive batches being; withdrawn from storage,'delivered to :the jacketed reactor, if used, or mixed with the desired internal. refrigerantgif the latter is used, and then polymerized by spraying the catalyst onto the surfaceofthe rapidly stirred cold mixture-or. preferably by delivering the catalystin the form of a fine high-pressure jet into the body of the cold unsaturates.

The amount of catalyst added is determined by the-conversion desired. 'It will be noted that since-the conversion is measuredin terms of the amount-of isobutylene, not upon the total amount of unsaturates present, the desirableamount of eatalyst'issuch as to yield a polymer having a weight equal to from /5 to the full amount of isobutylene present. This procedure leaves in the polymerizate mixture aconsiderable quantityv of unpolymerized butadiene, and a small quantity of isobutylene. *Itis' made necessary, however, by the fact that the higher polymerizability ofthe isobutylene compared to the butadiene results in a mixture in which the butadiene ratio is so high that the polymer is undesirably close to being-a pure butadiene polymer which, as is well known to workers skilled in the art, is of little'or no value. When the desired amount of polymer has been produced, the reaction mixture with the contained polymer is preferably dumped into warm water to bring the solid polymer up to room temperature and vaporize out the residual materials from the polymerization mixture. c

Alternatively, if the reaction is conducted in a continuous manner, the reactor is filled with an appropriate mixture of unsaturates which may be the same as the equilibrium mixture obtainablein the reactor after continued operation, or

is brought into actionto circulate the material over the cooling jacket walls as rapidly as possible, and the injection of catalyst is thenbegun.

Preferably,.the reactor is closed with a tight cover having an appropriate size tubular outlet, so that the'reactor is full at all'times, and there is no liquid to gas interface in the reactor. The supply streams of unsaturate mixture and catalyst are continued and an overflow of polymer slurry or solution (depending upon diluent) in unpolymerized material is taken out through the overflow tube and preferably delivered into'a closed tank of warm water in which the slurry of polymer in cold feed is converted into a slurry in warm water and the voltatile components of the mixture are vaporized and discharged from the top vof the water tank to purifying and fractionating equipment by which they are recovered for re-use.

The solid polymer is discharged from the tank asa slurry in 'water from which it is filtered,

low 0.1%.

dried, and milled. for. packaging, shipping and use.

Either processing method yields a polymer havingl-aistaudinger.molecular: weight number lying within. the range between about 20,000 tor-25,000 and-about 80,000to 1 00,000. This range iisaessentialubecause' of theyfact that polymers. having lower im'olecular weights :either do. .not care at all, 'oncure toopoorly. to be commercially useful andpolymers having molecular. weights higherv than this range'are so tough and leathery that they are extremely difficult-to process on the mill. It. may be noted that there is a fairly wide range of molecular weights in the polymer; a. polymer havingamoleeular weight of 35,000:showing a smallamount of material of molecular weight as low "as-20,000 and a small .amount as high as 60,000 .or 70,000.. This range of molecular weights depends in part uponthe temperature, in part upon the catalyst, and in part upon the :proportion oiisobutylene and ;butadiene. The polymer also shows an iodine, number within the-range between about. 60 and aboutil50; the iodine number being in part determined by the original pro.- portionebetween the mono-olefin: and the multiolefin, and in part determined by the percentage yield; orthepercent of the unsaturates-which areeopolymerized. r I I The .polymer obtained.,n1ay be subjected to a considerable rangeoi :subsequent treatments. If the polymer is madelin acontinuous pro'cess,'the discharged polymer and unsaturatemixture from the .polymerizerthroughanoverflow outlet into a5 tankof hot water .yieldsa slurry of polymer in water which :can conveniently be handled through pipes, and pumps, a centrifugal type of pump usually being preferred. The slurry may then be filtered or strained, using such devices as ani Oliver type filter, in which the. carrying I liquid is removed by'suetion and a:so1id'cake scraped off the :exterior of a strainer-meshcovered drum. The-water is conveniently heated and returnedto the flash tank forthe formation or" fresh slurryythisbeing particularly'desirable because of the fact that the straining-operation .does not always separate all of the solid polymer, but allows some of the fine particles to pass through. The solid cake'from thepfilter is .con- -veniently delivered to a traveling belt passing through a tunnel drier. oven. The "drying operation usually brings the water content well below 1%,. and for J some purposes. this. *issufiicient.

.Usuallys-however, it is preferablylto take the 'cake from the oven,.off the end of the travelin belt; and pass :it through a high power extruder in which the-polymer is heated to .a temperature well above the boiling point oiiwater, and, at that temperature is extruded ins-small strings. This; procedure brings the water content well be- For operating convenience and toreinoye substantially all of such residualmoisture "and anytracesof unevaporated volatiles, and

also to make sure that any lowpolymers are removed, the extruderi discharge may conveniently be treatedon a clouble roll mill and given a some- -is cooled-and out into short lengths andpacked in boxes.

- The finished polymer is thenrprepared for'use by an appropriate compounding. treatment. f It i usually desirable to incorporate a substantial amount of reinforcing carbonblack. "Any. of the .various typesoficarbon black areiusefulfaccord- ,fai rly rapidly at room temperature.

ing to the;particularrstructurefjto.heamadei-from the rubber. However, when 'inner-tubes rare to be made itis usuallyzdesirable' to use a reinforcing carbon black such as the type .thatis described 110. the trade: by the descriptive. title xicabottNo; 9. Alternatively; another type of reinforcing: carbon black or furnace black, known .to eompoEunders by the descriptive name fKosmobileI66"I alsods .ad: vantageously used. l The carbon black i may'zbe present in amounts from. 10 :parts a to. parts per 100 of polymer and on occasion-asimuchvas 200 parts may be used. The compounding recipe also desirably includes f-rom'0.5: part ito' 10:.parts of stearic acidper 1000f polymer. In addition there usually isdesirably present from lipart to about 20 parts of zin('r--oxide;- which *m a r; on occasionbe replaced by -var ying amounts, "up to about 10 parts, ofzinc" stearate; 1 l

"The compoundin recipe alsoincludesa curing agent. Sulfuralone is not usually comniercially satisfactory because of theextremely" slow' curing rate and'the difficulty or 'reaching a complete cure. Acco'rcling'lya sulfurization aid 'or accelerator is usually 'in'cluded; --'This'= mayeonveniently "be tetramethyl tliiuraln disulflde which, however, may be used- 1n consider'ably smaller proportions than is required by thelow'-u-risatura-'- tion. polymer er the prior- 'artf -Alter natively, however, such agents as jnercaptobenzotliiazole or zinc mercaptobenzo'thiazoleorfselenium tetraethyl dithiocarbamatefor' tetrameth'yl" thiura'rn monosulfide or zinc dibutyl' dithiocarbamate "or dipentam'ethylene" thiura'in tetrasulfide; inay be used. Any of theseagents most oi whichare o'f minor or no "value'witnthe flow; unsaturation polymers of the" prior "art are more or less va'lu able with the present polymer, ais ar .iAlternatively also, dinitrosocornpounds' are valuable curin agents andlfwithfjzthese compounds, particularly, he. curingfn' ay' proceed These agents'all reactwithftlie'lniatei ial d?- stroythe plasticity -whicli,is characteristic oflthle po me a tl v dffism therpol ynie iz .or the, drier and{develop in it a.;definite tensile strength and a definite elongation at. break a definite modulus; of elasticity (that is l 'the pounds pull per square inch require dl'to. stretch the material 30 0 %1') 1aracteristiC,.'.D 'uS a substantially s mple e {1m oliibility' ,ras' eis tinguished from swelling) in light haplithaare the essential features" of the{ cured .polynierl as square inch up 00 3600 -pounds' or' higher, with relatively high modulus and theparticularly valu- -"able characteristic? of a very ra'pid' touring .rate, to a more fully cured: condition; Also, the'poly- :mer of thepresent: :inventioncan be. curedto. a I good tensile strength and: a. good modulus; With- L out, of necessity; establishing; a-rconditiomoi aero eimo's't of the iodine number, thereby further reactions.

The details of the invention are well shown by the following examples.

EXAMPLE 1 A series of polymerizations'were conducted upon successive batches of polymerizate containing varying amounts of butadiene in ratios to isobutylene ranging from 1.8 to 27, both substances having a purity of 98% or better. These polymerizations were conducted with isobutane as diluent, approximately three volumes of isobutane being used for each volume of isobutylene. The various batches were polymerized in part only, from 16% to 29% of the isobutylene being polymerized in the various runs. In each polymerization procedure the mixture was cooled to nearly 103 C. by the application of a refrigerating jacket containing liquidethylene to the reactor.

The catalyst consisted of a solution of aluminum chloride in methyl chloride in a concentration of approximately 0.2%, the catalyst solution being added to the reaction mixture in the form of a high pressure jet into the body of the rapidly stirred cold mixture.

making possible some 10 warm water. The diluent and unpolymerized unsaturates were volatilized by the warm water and the solid polymer was then strained out from the water, dried and milled.

After milling, each batch of polymer was separately compounded according to the following recipe:

Parts Polymer 100 Gastex Zinc oxide 5 Sulfur 2 Accelerator, as indicated.

Separate portions from each batch were then further compounded with sulfurization aids, as

' TABLE II Cures at 307 F.

Accelerators l Tensile Elongation 300% Modulus Q.

3 4 510 "iIib' 1, 390 510 420 390' 320' 840 1, 090

Cures at 320 F.

Tensile Elongation 300% Modulus S=Benzothiazyl 2-monocyclohexylsulfenamide one part based on polymer.

TC=Tetramethyl thiuram disulflde.

The inspection reports upon these batches of polymer are shown in the following Table I:

. TABLE I Isobutylene -Butadiene Copolymers of High Unsaturation 1 (completely soluble in hydrocarbons) 1 Feed (parts C I onver- Staud. butadlene Diluent sion per- Mol. Iodme per 100 of cent 3 Wt No. isobutylene) 1 180 Isobutane 3:1 29 30, 200 52 2 210 .do 16 26,200 58 3 210 do 24 20, 200 4 240 do 18 25, 400 57 5 270 -do 16 ,400 72 6 240 None 27 65 A1] polymers prepared in batch reactor at '100 C. using A101 dissolved in MeCl (0.2 g. AlCla/IOO ml. MeCl).

Volumes of isobutane per volume of isobutylene.

Based on isobutylene.

These various polymers were recovered by dumping the partially polymerized mixture into One part and mercaptobenzothiazole 0.5 part.

These results show the excellent quality of the polymer obtained by this procedure and the excellent curing rate, tensile strength, elongation at break, and modulus obtainable.

These results also show the very greatly increased rate of cure of this relatively highly unsaturated copolymer. In Table II there is shown, for comparative purposes, the rate of cure of the low unsaturation copolymer of isobutylene with isoprene produced under the direction of the Rubber Reserve Board for the use of the armed forces of the United States under the descriptive title of GR-I. It will be noted that the polymer of the present invention cures much more rapidly than does the standard GR-I. It will be noted from this table that in 10' #1 goes to 1540 modulus and GR-I goes to 140. Thus the highly unsaturated polymers gave eleven times higher modulus than GR-I at the same cure time, In effect this means that polymers of this nature canbe cured without high concentrations of expensive accelerators such as tetramethyl thiuram disulfide or a satisfactory cure can be obtained by the use of cheaper accelerators such as bon zothiozyl 2-monocyclohexylsulfenamide (Santocure) or similar accelerators of lower potency.

EXAMPLE 2 A similar series of batch polymerizations were conducted as shown in Table 3, using mixtures containing from 24 to 9% O1 isobutylene, and

from '76 to 91% of butadiene; some utilizing normal butane as the diluent, some methyl chloride, and in some instances no diluent. In each instance the conversion is based on isobutylene although a considerable amount of the butadiene is copolymerized as evidenced by the iodine numher or by material balance. For example, the last polymer in Table III contained at least 50 butadiene copolymerized with the isobutylene.

TABLE III ularqweight number within the range between- 20,000 and 100,000, an iodine number withinthe range between 60 and 1'75 and reactivityrwith curing agents such as-sulfur, the quinone dioximes and the dinitroso compounds to yield a cured polymer having a tensile strength within therange between 1000 and 4000 pounds per square inch.

While there are above disclosed but a limite number or embodimentsofthe composition and process of the invention, it is possible to provide. still other embodiments without departing .fiOnl the inventive concept herein disclosed.

The invention claimed is: 1. A low temperature polymerization process which comprises mixing 91 parts by weight of butadiene, 9 parts by weight of isobutylene and 2.5 volumes of normal butane per volume ofisobutylene, cooling themixture to a temperature of about 103 C. and adding thereto a solution IsobutyZene-butadiene copolymers of high im-v saturation (not completely soluble in hydro- 1 Conversion on total feed 18%-assuming all isobutylene .copolynie'rized the polymer contains 50% isobutylene+50% butadiene.

The copolymerizability ratio above-mentioned may be defined as the relationship between the amount of diolefin in the polymer divided by the amount of olefins in the polymer, the result be ing divided by'the weight'of diolefin in the reactor liquid divided by the weight of olefin in the,

reactor liquid or mathematically, the copolymeri zation ratio a may be defined by the following equation;

weight diolefin in copolymer Weight olefin in copolymer- (1:: weight diolefin in reactor liquid weight olefin in reactor liquid Plant experience shows that for isoprene the value or a is 0.5 to 1 whereas for butadiene the value of a is frm.0.025 to 0.048.

Thus the process of the invention prepares a mixture of isobutylene and butadiene in which the butadiene is present in the ratio of at least 1.8, theratio of the invention ranging from 1.8 to or 12, to which there is then added, if desired, from 1 to 5 or 6 volumes of inert diluent which is liquid at the reaction temperature and. the mixture with or without diluent is then polymerized at a temperature within the range between 40 C. and l10 C. by the application to the cold isobutylene-butadiene mixture of a Friedel-Crafts active metal halide catalyst in solution in a lowfreezing, non-complex-forming solvent such as aluminum chloride in solution in methyl chloride to yield a copolymer havin a Staudinger moleccontaining-about 0.2 grams of aluminum chloride per 100 ml. of methyl chloride to obtain a rubberlike copolymer having an 8-minute Mooney Viscosity of at least about 25 at 100 C.

2. A low temperature polymerization process comprising the steps of mixing together 1 part by weight of monomeric isobutylene and 1.8 to 10 parts by weight of monomeric butadiene, cooling the mixed olefinic material to a temperature within therange-between -40 C. and 164 C., and thereafter polymerizing the mixture to at least 20% conversion based on the total isobutylone by the application thereto of a Friedel-Crafts active metal halide catalyst in solution in a lowfreezing, non-complex-forming solvent.

3. A low temperature polymerization process comprising the steps in combination of preparing. a mixture of 1 part by weight of isobutylene monomer and 1.8 to 10 parts by Weight of butadiene monomer, delivering a continuing stream thereof to a reaction zone at a temperature within the range between 40 C. and -l64 0.,

simultaneously delivering to the reaction zone a continuing stream of a solution of an. aluminum halide catalyst" dissolved in a low-freezing;

halogenated alkane having 1 to 2 carbon atoms per molecule as solvent to polymerize the mix ture to at least 20 conversion based onthe total isobutylene, collecting an overflow from-thesaid' reaction zone in a warm'liquid 'tovolatilize out the reactants to produce a copolymer.

4. A synthetic, solid, rubber-like interpol-ymer of butadiene and iso-butylene, characterized by'a ready vulcanizability to a cured synthetic rubberhaving a tensile strength of 1,0004,000 pounds per square inch, and an elongation of 150-1,000%.

6. A low temperature polymerization process comprising the steps of mixing together 1 part by weight of isobutylene monomer and 1.8 to parts by weight of butadiene monomer, and 1 to 6 volumes of inert diluent per volume of isobutylene, cooling the material to a temperature within the range between -40 C. and 164 C'., and thereafter polymerizing the mixture to a conversion of to 90% based on the total isobutylene, by the application thereto of a solution of aluminum chloride in an alkyl chloride of 1 to 2 carbon atoms to obtain a copolymer having a Staudinger molecular weight between 20,000 and 100,000, and an iodine number between 60 and 175 as measured by the Wijs method.

7. A low temperature polymerization process comprising the steps of mixing together 71 to 91 weight per cent of butadiene monomer and 29 to 9 weight per cent of isobutylene monomer, cooling the material to a temperature within the range between C. and 164 C'., and thereafter polymerizing the mixture to at least 20% conversion based on the total isobutylene by the application thereto of a solution of aluminum chloride in methyl chloride until a copolymer is obtained having a molecular Weight between 20,000 and 100,000, and an iodine number between and 175 as measured by the Wijs method, and having 10-70% of combined butadiene and 90-30% of combined isobutylene.

8. A synthetic, solid, rubber-like interpolymer of 10 to combined butadiene and to 30% combined isobutylene, characterized by a Wijs iodine number between 60 and 165, a Staudinger molecular weight between 30,000 and 100,000 and ready Vulcanizability to a synthetic rubber hav= ing a modulus of about 1300 to 1540 pounds per square inch at 300 elongation.

JOSEPH F. NELSON. LESTER MARSHALL WELCI-I.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,180,082 Cunradi Nov. 14, 1939 2,305,007 Hopff Dec. 15, 1942 2,356,128 Thomas Aug. 22, 1944 2,476,000 Sparks July 12, 1949 OTHER REFERENCES Kemp et al., Ind. Eng. Chem, Anal. Ed, 15, pps. 453-459 (July 1943). 

8. A SYNTHETIC, SOLID, RUBBER-LIKE INTERPOLYMER OF 10 TO 70% COMBINED BUTADIENE AND 90 TO 30% COMBINED ISOBUTYLENE, CHARACTERIZED BY A WIJS IODINE NUMBER BETWEEN 60 AND 165, A STAUDINGER MOLECULAR WEIGHT BETWEEN 30,000 AND 100,000 AND READY VULCANIZABILITY TO A SYNTHETIC RUBBER HAVING A MODULUS OF ABOUT 1300 TO 1540 POUNDS PER SQUARE INCH AT 300% ELONGATION. 